1. Field of the Invention
The present invention is generally concerned with artificial optical lenses, that is to say contact lenses or intra-ocular implants and ophthalmic lenses, that is to say eyeglass lenses, and it is more particularly directed to artificial lenses which have a radial profile of specific power to obtain a specific corrective action.
2. Description of the Prior Art
Contact lenses are currently manufactured by molding or by machining.
The advantage of molding is that the required power profile is obtained directly, by simple duplication of an appropriate mold.
However, only the external radius of curvature of the manufactured artificial contact lenses can then be varied, their inside radius of curvature having to remain within narrow and closely specified limits to achieve a good match to the radius of curvature of the cornea of the patient.
Manufacture by molding therefore requires that a large number of different molds be available.
These molds must cover all the ranges of powers required to correct all forms of ametropia.
In the case of contact lenses for correcting long sightedness, the molds must also cover all ranges of additional powers needed to correct all forms of long sightedness for each variety of ametropia to be corrected.
Manufacture by machining starts with a molded semi-finished product which is then mechanically processed to confer upon it the required power profile. This has the advantage of reducing the number of different molds required.
In practise, however, considerable processing has to be applied and is delicate and costly.
It has previously been proposed to apply physical-chemical processing to optical lenses.
This is the case, for example, with the published French patents Nos 2 029 178 and 2 076 194.
However, these French patents are essentially concerned with the manufacture of corrective lenses to be fitted to eyeglass frames. Although the first patent refers to the possibility of irradiating contact lenses, the irradiation is in practise by means of neutrons and its only purpose is to eliminate certain defects of the contact lenses.
These French patents are therefore not concerned with the manufacture of artificial optical lenses having a given power profile.
The Japanese patent document No JP-A-61 053031 proposes the use of physical-chemical processing to obtain a particular power profile, using a mask to achieve spatial modulation of the flux of energy to be controlled, but the initial substrate is merely a parallel sided slab.
The mask employed is also a static mask, which operates in terms of levels of grey, so to speak, and the blackening of which is in fact difficult to control.
A particular object of the present invention is a method for manufacturing an artificial optical lens with any given power profile that is advantageously free of these disadvantages.